Pathophysiology
Clinical meaning
Massive hemorrhage protocol (MHP) is a structured, institution-wide response to life-threatening hemorrhage, defined as loss of one blood volume within 24 hours, 50% blood volume loss within 3 hours, or ongoing bleeding at greater than 150 mL per minute. The physiological cascade of hemorrhagic shock progresses through compensated (Class I-II: tachycardia, vasoconstriction maintaining blood pressure), to decompensated (Class III-IV: hypotension, altered mental status, metabolic acidosis) stages. The lethal triad of trauma -- hypothermia, acidosis, and coagulopathy -- creates a vicious cycle: hypothermia impairs coagulation factor enzymatic activity, acidosis inhibits clotting factor function and reduces fibrinogen levels, and dilutional coagulopathy from crystalloid resuscitation further impairs hemostasis. Damage control resuscitation emphasizes balanced transfusion with a 1:1:1 ratio of packed red blood cells, fresh frozen plasma, and platelets, permissive hypotension (systolic 80-90 mmHg in non-TBI patients), minimal crystalloid use, calcium replacement (citrate in blood products chelates calcium needed for coagulation), and tranexamic acid administration within 3 hours. The nurse activates the MHP per protocol, establishes large-bore IV access, administers blood products through rapid infusers with warmers, monitors coagulation labs (TEG/ROTEM for point-of-care guided...